Friction ignitor



Dec. 17, 1968 BALLRElcH ET AL FRICTION IGNITOR Filed Oct. 18. 1966 INVENTORS KURT BALLREICH ALFRED KETTERL WOLFGANG SPRANGER ATTORNEYS United States Patent 3,416,450 FRICTION IGNITOR Kurt Ballreich, Nurnberg, and Alfred Ketterl and Wolfgang Spranger, Furth, Germany, assignors to Dynamit Nobel Aktiengesellschaft, Troisdorj f, Germany Filed'Oct. 18, 1966, Ser. No. 587,482 Claims priority, application Germany, Oct. 28, 1965,

D 4 Claims. (Cl. 10240 ABSTRACT OF THE DISCLOSURE A friction ignitor provided with a coiled pull ignitor wire to frictionally ignite a primer charge, which in turn ignites a detonating charge; a plurality of meltable, preferably spherical lead, particles are placed between the coiled end of the wire and the detonating charge to be melted by and flow under the influence of the temperature and pressure of the burning detonating charge to seal the end of the cartridge case where the wire passes therethrough.

Background of the invention Summary of the invention Accordingly, it is an object of the present invention to provide a friction ignition device which eliminates the drawbacks encountered with prior art constructions.

Another object of the present invention is to provide a friction ignition device which prevents the combustion gases and other burning particles from escaping from the ignitor to the outside.

A further object of the present invention is to provide a friction ignitor that assures completely satisfactory ignition as well as reliable operation at all times.

Other objects and further scope or applicability of the present invention will become apparent from the detailed description given hereinafter; it should be understood, however, that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.

Pursuant to the present invention, it has been found that the above-mentioned disadvantages can be eliminated and a much improved friction ignitofr may be obtained if the friction ignitor is designed suchgthat after the actuation of the friction wire, combustion gases and burning particles are prevented from escaping to the atmosphere. The friction ignitor of the present invention comprises a cartridge having a friction end and a detonating end, and a friction wire, said friction wire having a coiled end portion and an uncoiled portion. The coiled end portion of the wire is disposed on the inside of the cartridge and extends toward the detonator end of the cartridge. The uncoiled portion extends from the coiled portion through the friction end of the cartridge to the outside of the friction ignitor, A priming material is provided between the coiled end portion of the wire and the friction end of the car- 3,416,450 Patented Dec. 17, 1968 tridge. A plurality of particles composed of a material melting at a low temperature, :such as for example, lead, is disposed adjacent the coiled end portion of the friction wire and partially fills the detonating end of the cartridge. Advantageously, the particles are spherically shaped. An additional detonating charge, ignition reinforcing charge, delaying charge, or other type of charge is disposed between these spherically shaped particles and the detonating end of the cartridge.

In a friction ignitor such as described above, the pulling of the friction wire ignites the priming material which in turn ignites the additional detonating charge. This additional charge quickly and reliably ignites the main charge to be detonated, for example, a pyrotechnic mixture, and also provides sufficient heat to melt the spherical particles inserted in the cartridge. As a result of the excess pressure produced by the heat of reaction, the molten spherical particles are pressed into and around the sleeve of the detonating means within the cartridge, where after a very short time they solidify, closing the opening produced by pulling the friction wire. Thus, the exit of combustion gases, or the ejection of burning particles from the ignited charge is substantially eliminated.

In a further embodiment of the present invention, one of the spherical particles used in the cartridge is made substantially larger than the remaining particles, for example, with a diameter of at least about of the inside diameter of the ignitor sleeve. This larger particle is inserted in the ignitor cartridge with part of its spherical body extending into the inside cross section of the coiled end portion of the friction wire. The remaining smaller particles can be grouped around the larger particle and extend in the direction of the additional detonator charge. While the large particle insures that a suificiently thick and well sealing layer of material is deposited on the bottom of the priming end of the detonator cartridge, the material represented by the remaining particles effects sealing between the detonator cartridge and the sleeve for the priming substance. Besides lead, which is the preferred material used in making the particles, other materials melting at still lower temperatures may also be used, such as for example, low temperature metal alloys.

According to a further embodiment of the present invention, an improvement in the sealing effect can also be obtained by providing at one end of the cartridge a disk of thermoplastic synthetic material, preferably polytetrafluoroethylene (Teflon). Thisdisk is adapted to the inside cross section of the ignitor cartridge and is provided with a correspondingly dimensioned central bore for passing the friction wire therethrough.

Since the friction ignitor is generally completely surrounded by the main charge to be ignited and thus the fixed positioning of the additional detonator charge in the interior of the ignitor cartridge is automatically determined, it is generally suitable if the ignitor cartridge is slightly drawn in at the end facing the charge to be ignited. However, in many cases, it proves advantageous or even necessary, to close the detonator cartridge at its end facing the charge to be detonated. This can be accomplished in a simple manner by means of a folding closure. For achieving a completely tight seal, a lacquer coating or the like can be additionally applied to the closure.

The additional detonator charge can be any easily ignitable mixture, such as, for example, a mixture containing about 60 parts by weight of lead dioxide and about 40 parts by weight of metallic silicon.

Brief description of the drawing The present invention will be more apparent when referring to the accompanying drawing which shows in a single figure, for purposes of illustration only, one embodiment in accordance with the present invention.

Detailed description of the drawing Referring to the single figure of the drawing, friction pull ignitor wire 5 passes centrally through the bottom of the cartridge and its spirally wound end is inserted in the ignitor cartridge 1. The other end of the wire, located outside the cartridge, is shaped in the form of a loop. Between the bottom of the cartridge and the coiled end portion of the friction wire there is successively provided disk 2, which may be made of a thermoplastic material, such as, for example, Teflon, an intermediate disk 3 and a friction primer material 4. All of these elements are provided with a central bore for passing the friction wire therethrough. A large spherical particle 6, which can be made of lead or some like material, partially extends into the coiled end portion of the friction wire and is disposed toward that end of the cartridge facing the main charge to be detonated, this charge not being shown. Following the large particle, small particles 7 are distributed over the inside cross section of the ignitor cartridge 1. The remainder of the space in the ignitor cartridge is filled with an additional detonator charge 8 and the end of the cartridge is closed off by means of fold 9 and sealed by means of the lacquer coating 10 at the tip of the fold.

If the friction wire is quickly pulled in the customary manner, the primer cap 4 at first ignites the additional detonator charge 8. The latter then ignites the main charge which is to 'be detonated, this charge not being shown in the drawing. Simultaneously, the heat developing during the reaction of the additional detonator charge 8 effects the melting of the particles 6 and 7. The molten mass is pressed into and around the primer 4 remaining in the ignitor cartridge 1, by the excess pressure produced by the heat of reaction. At these places the molten mass solidifies again very rapidly and forms a gas-tight seal for the opening produced by pulling the friction wire.

Since modifications of this invention will be apparent to those skilled in the art, it is not desired to limit the invention to the exact constitution shown and described. Accordingly, all suitable modifications and equivalents may be resorted to which fall within the scope of the appended claims.

We claim:

1. A friction ignitor, comprising: a cartridge case having a friction end and a detonating end; a friction pull ignitor element partially inside of said cartridge case and extending through the friction end of said cartridge case; a primer charge within said cartridge case adjacent and to be frictionally ignited by said pull ignitor; a

detonating charge between said pull ignitor and said detonating end of said cartridge case to be ignited by said primer charge; non-ignitable means having a melting temperature substantially lower than the burning temperature of said primer charge and said detonating charge to at least partially melt and flow under the infiuence of the temperature and pressure of the burning detonating charge for sealing the friction end of said cartridge case.

2. The friction ignitor according to claim 1, wherein said pull ignitor is a wire having one end coiled within said cartridge case; said non-ignitable means is a plurality of particles resting on said. coiled end between said coiled end and said detonating charge.

3. The friction ignitor according to claim 2, wherein said particles are spherical.

4. The friction ignitor according to claim 2, wherein one of the particles is substantially larger than the other particles and has a diameter of at least about of the inside diameter of the ignitor cartridge case.

5. The friction ignitor according to claim 4, wherein the larger particle partially extends into the coiled end portion of the friction wire.

6. The friction ignitor according to claim 2, wherein the particles are lead.

7. The friction ignitor according to claim 2, wherein the friction end of the cartridge case is provided with a disk of thermoplastic synthetic material which is adapted to the inside cross section of the ignitor cartridge case and is provided with a central bore through which the friction wire extends to the outside.

8. The friction ignitor of claim 7, wherein the thermoplastic synthetic material is polytetrafiuoroethylene.

9. The friction ignitor of claim 1, wherein the detonating end of the cartridge case is closed by means of a folding closure.

10. The friction ignitor of claim 9, wherein the tip of the folding closure is tightly sealed by means of a lacquer coating.

References Cited UNITED STATES PATENTS 379,147 3/1888 Andrews 102-70 3,000,311 9/1961 Stanley 102-70 3,060,854 10/ 1962 Maretti 114-20 X FOREIGN PATENTS 671,286 10/ 1963 Canada.

ROBERT F. STAHL, Primary Examiner. 

